UPDATE: After testing and further consideration, we have determined that the best place to measure query and click traffic from Google Images is in the Search Console Performance Report. Accordingly, we will continue to use https://www.google.com (or the appropriate ccTLD) as the referrer URL for all traffic from Google Images, and will not be providing a Google Images specific referrer URL (images.google.com).

Again, I think Google changed this last April but the update is not labeled with a timestamp, so I am not 100% certain when Google decided not to go through with this.

For those who have already updated their analytics tools to handle it, you can undo that change - sorry.

Hat tip to AJ Kohn for spotting this:

I kept waiting for Google to roll out the image referrer in Google Analytics. But it turns out they decided not to after "further consideration". Am I the only one who missed this post update? pic.twitter.com/aU8wkRUsxr